Interpass: Uninterrupted, Grade-Level Interchange having One-way Approach and Departure Legs

ABSTRACT

The Interpass: Uninterrupted, Grade-Level Interchange having One-way Approach and Departure Legs is a geometric design for an at-grade interchange of one-way roadways that has no conflict points and which allows uninterrupted, uniform-velocity traffic flow. The subject invention is neither an overpass, nor an underpass, nor an at-grade intersection, nor a grade-separated interchange, and it has comparatively few of the negative qualities associated with those types of roadway junctions. Uninterrupted, grade-level interchanges of the subject design, when connected into a directed transportation network having one-way roadway segments, can constitute the nodes of an intrinsically-safe, grade-level, arterial or collector transportation facility with superior controllability, efficiency and safety, compared to those of traditional facilities.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX

Not Applicable

BACKGROUND OF THE INVENTION

The subject invention falls into the following classifications, which were included in the fields of search for related patents and applications:

Cooperative Patent Classification (CPC) E01C 1/02

-   -   E (Fixed Constructions)     -   E01 (Construction of Roads, Railways or Bridges)     -   E01C (Construction of, or Surfaces for, Roads, Sports Grounds,         or the like; Machines or Auxiliary Tools for Construction or         Repair)     -   E01C 1/02 (Crossings, Junctions or Interconnections between         Roads on the Same Level)

US Classification 404/1

-   -   404 (Road Structure, Process or Apparatus)     -   404/1 (Static Structures)

The subject invention pertains to the field of traffic engineering and to the design of vehicular transportation systems. A vehicular transportation system provides a framework within which vehicles move to carry passengers and objects efficiently and safely between locations. The physical structure of a vehicular transportation system is a transportation facility, and can be thought of as a spatial network of nodes connected by segments, wherein the segments typically represent roadways, and the nodes, roadway junctions.

Networks of roadways and junctions are functionally classified as either urban or rural, and are sub-classified according to the scope of the area served and access management level as either terminal (parking), local (terminal access such as residential streets, alleys and cul-de-sacs), collector (collection and distribution of traffic from local roadways), arterial (minor arterials surrounding city blocks; principal arterials forming city avenues and boulevards), or high-speed divided multilane (highways, expressways having partial access control; freeways having full access control).

Roadway segments (roadways) define, and form the boundaries of, vehicular traffic paths. Roadways may have one or more parallel lanes (carriageways), and may be either one-way (allowing traffic flow in one direction), or two-way (with at least two of the lanes having traffic flow in opposite directions). Lanes may be classified as either soft, meaning that vehicles are permitted to cross the lane boundaries to move between (i.e. change) lanes, or hard, meaning that vehicles are restricted to stay within a single lane.

A roadway junction is the portion of a transportation facility in the vicinity of a point (a network node), toward which two or more traffic paths (segments) converge horizontally. An intersection is a special case of junction in which converging traffic paths physically intersect. Other types of junction, such as overpasses, underpasses and interchanges, have horizontally-converging traffic paths that are physically separated or routed so as not to intersect. There are many geometric configurations of roadway junction, each with a unique set of functional characteristics, safety features and constructability challenges.

A traffic interchange (interchange) is a roadway junction that allows vehicles to change from one roadway to another, to select between different directions of travel. An interchange can be qualitatively classified with respect to network connectivity in terms of its “interchange density” thusly: a “sparse” interchange is a junction for which at least one of the inbound traffic paths has only one choice of outbound traffic path; an interchange of minimum density “M” provides each inbound traffic path at least M choices of outbound traffic path; a “saturated” interchange connects each inbound traffic path with every possible outbound traffic path.

Vehicular collisions account for the majority of bodily injuries and property damage that occur within roadway systems. Therefore, the primary safety concern in the design of transportation facilities is with the prevention of vehicular collisions. Traffic flow is controlled to minimize collision potential by separating traffic either temporally or spatially so that no space should ever be occupied by more than one vehicle simultaneously.

A conflict occurs at any point along a vehicular path through which two vehicles could pass, and at which those vehicles could collide with a relative velocity sufficient to cause substantial property damage or injury, if a failure of traffic controls were to occur. The most common examples of conflict points are the crossing intersection of two vehicular paths and the intermittent stop. Gradual lane changes among vehicles having approximately-equal velocities do not constitute conflict points. Speed-change ramps serve to eliminate conflicts by allowing traffic to accelerate to match traffic velocity prior to entering a through-travel roadway (note: the term “ramp” in this context does not necessarily imply a grade-level change).

High-speed, divided-multilane transportation facilities are designed using interchanges and speed-change ramps to eliminate conflicts such as crossings and intermittent stops, and to allow uniform-velocity traffic flow along continuous lanes and lane changes that can be made at low relative velocities. A transportation facility having no conflict points, within which traffic may flow continuously at a uniform velocity, is uninterrupted.

An uninterrupted transportation facility having no conflict points, within which traffic may flow continuously at a uniform velocity is also intrinsically-safe. Intrinsic safety relies on nothing more than the static safety features of the facility, i.e. those safety features that unconditionally accommodate dynamic changes in traffic flow. Transportation facilities having conflict points are not intrinsically-safe and require extrinsic safety features, such as engineered Traffic Control Devices (TCD) or administrative safety procedures to interrupt traffic flow at conflict points and mitigate the potential for collisions to occur. Traffic Control Devices include signage, signals, markings, barriers, sensors, controllers, and other control elements that direct vehicles to alternately yield or proceed using combinations of complete stops, merging/diverging procedures and timed movements. Administrative safeties include laws, regulations, safety rules, warnings, etc., which vehicle operators are expected to interpret and apply as appropriate to each situationally-specific traffic condition. Any failure of an extrinsic traffic safety feature could expose a conflict point and create the potential for a collision to occur.

A traffic intersection (intersection) is a type of junction having at least two vehicular paths that either cross each other or otherwise intersect, vertically and horizontally, to form a conflict point. As such, no intersection is intrinsically-safe, and every intersection must rely upon extrinsic safety features to eliminate the potential for collisions. One example of a traffic intersection is the conventional two-lane, four-way box intersection, which has thirty-two conflict points (eight merging, eight diverging, and sixteen crossing).

Some common examples of intersection geometries include:

-   -   1. 4-way Stop     -   2. Box Junction     -   3. Staggered Junctions     -   4. Turnarounds     -   5. Michigan Left         -   a. Michigan Loon         -   b. Median U-Turn (MUT)         -   c. Median U-turn Crossover         -   d. Boulevard Left         -   e. Boulevard Turnaround         -   f. ThrU Turn Intersection         -   g. Jughandle Left     -   6. Reduced Conflict Intersection     -   7. Pittsburgh Left         -   a. Boston Left         -   b. Massachusetts Left         -   c. New Jersey Left         -   d. New York Left     -   8. Texas Turnaround         -   a. Texas T         -   b. Texas U-Turn     -   9. Superstreet     -   10. Restricted Crossing U-turn (RCUT)     -   11. Hook Turn     -   12. J-Turn     -   13. Right-in, Right-out (RIRO)     -   14. Split Intersections     -   15. Seagull Intersections (Continuous Green T)     -   16. Synchronized Street     -   17. Quadrants     -   18. Slip Lanes     -   19. Advanced Stop Lines.     -   20. Continuous-flow Intersections (CFI)         -   a. Displaced Left Turn (DLT)         -   b. Crossover Displaced Left Turn (XDL)         -   c. Parallel Flow Intersection (PFI)

A geometric special case of the intersection is the traffic circle, by which an attempt is made to allow continuous traffic flow without the use of Traffic Control Devices (TCD), but which requires administrative safety procedures and driver dexterity to mitigate conflicts that arise from abrupt merging-, diverging-, speed-change and lane-change operations (increasingly so with increasing traffic loading). Traffic circles include variants such as:

-   -   1. Roundabouts     -   2. Bowties     -   3. Mini-Roundabouts     -   4. Turbo Roundabouts     -   5. Rotaries     -   6. Stop-controlled Circles     -   7. Traffic Signal-controlled Circles.

Intersections, in addition to having conflict points that give rise to the potential for collisions, present other hazards and difficulties, including:

-   -   1. that navigation within intersections can require complex         vehicular maneuvers, sometimes within a short distance and time,         demanding increased driver attention, reaction speed and         situational awareness, and elevating driver stress;     -   2. that Traffic Control Devices (TCD) are costly to implement         and maintain;     -   3. that administrative and engineered safeties can fail, with         potentially-dangerous results;     -   4. that administrative traffic controls fail more frequently and         have more complex and interdependent failure modes than do         engineered safeties;     -   5. that there is frequently a higher concentration of vehicular,         non-motorized and pedestrian traffic near intersections;     -   6. that traffic flow is slowed at intersections;     -   7. that travel time, fuel use, pollution and noise in the         vicinity of intersections are increased; and, perhaps most         importantly,     -   8. that occurrences of fatal traffic accidents are most heavily         concentrated at intersections.

One method of reducing conflict points at junctions is grade-separation, which is the displacement of traffic paths vertically to eliminate crossing/angle conflicts. The simplest examples of grade-separated junctions are overpasses and underpasses, wherein any conflict between crossing roadways is eliminated by spatially separating the roadways. Although simple overpasses and underpasses eliminate conflict points, they are not interchanges because they do not allow vehicles to leave one traffic path to join another, or to take more than one directional path. Overpasses and underpasses can form interchanges when joined with speed-change ramps to allow vehicles to change between roadways.

A grade-separated interchange is one wherein at least two horizontally-intersecting traffic paths are separated vertically to prevent the occurrence of one or more conflict points.

Some common examples of grade-separated interchange geometries include:

-   -   1. Three-way Interchanges:         -   a. Trumpet         -   b. Directional T         -   c. Full Y     -   2. Four-way Interchanges:         -   a. Cloverleaf         -   b. Stack or Butterfly Junction         -   c. Cloverstack         -   d. Turbine     -   3. Interchanges between freeways and surface roads:         -   a. Diamond         -   b. Parclo         -   c. Single-Point Urban Interchanges         -   d. Folded Diamond         -   e. Diverging Diamond (DDI/DCD)         -   f. Double Framed H-Interchange         -   g. Continuous Flow Interchange (CFI) with grade-separated             flyover             -   i. Displaced Left Turn (DLT) with grade-separated                 flyover             -   ii. Crossover Displaced Left Turn (XDL) with                 grade-separated flyover

Grade-separated interchanges having no conflict points can be applied as junctions for intrinsically-safe, uninterrupted transportation networks. However, grade-separated interchanges are costly to construct and maintain, require large swaths of real estate, and are noisy. For those reasons, grade-separated interchanges, though frequently found in high-speed divided multilane systems, are very rarely applied to primary/arterial surface roadways or collector streets. The vast majority of arterial and collector transportation facilities are at-grade.

The subject invention, the Interpass, is a geometric design for a traffic interchange that can be constructed entirely at-grade, thus avoiding the costs associated with grade-separations, but which, like grade-separated interchanges, provides the benefits of intrinsic safety and uninterrupted traffic flow, free of conflict points. The subject invention is neither an overpass, nor an underpass, nor an at-grade intersection, nor a grade-separated interchange, and it has comparatively few of the negative qualities associated with those types of roadway junctions.

Uninterrupted, grade-level interchanges of the subject design, when connected into a directed transportation network having one-way roadway segments, can constitute the junctions (nodes) of an intrinsically-safe, grade-level, arterial or collector transportation facility.

BRIEF SUMMARY OF THE INVENTION

The subject invention, the Interpass, is a geometric design for an at-grade interchange of one-way roadways that has no conflict points and which allows uninterrupted traffic flow. It is the objective that this invention:

-   -   1. Be applied as junctions (nodes), which can be connected         together by grade-level, one-way roadways (segments) to comprise         an at-grade, arterial or collector transportation facility         (network) which allows uninterrupted traffic flow from any point         on that network of roadways to any other point on that network         of roadways;     -   2. Provide an intrinsically-safe interchange having no conflict         points, with minimal requirements for extrinsic safeties such as         traffic control devices or administrative rules;     -   3. Provide an interchange that is easily adapted to an existing         infrastructure of perpendicular-grid arterial or collector         streets, without requiring grade-separations or substantial         increases of surface area;     -   4. Provide a well-connected interchange (minimum density 2) that         allows traffic on each roadway approaching toward a junction         point to select one from at least two options of roadway         departing away from that junction point.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

A plan view of a geometric design for a Double Interpass (uninterrupted, grade-level interchange with two inbound one-way approach legs), with each approach leg having two lanes, is shown in FIG. 1 on Sheet 1/5 of the drawings. The approach legs, on the west and east sides of the figure (with north represented as toward the top of the sheet) each split (bifurcate) as they approach the junction point (in the direction of traffic flow), with one lane turning to the right and the other to the left. Those lanes then continue to turn away from the junction point and depart away from the junction without having crossed, or otherwise intersected, any other lane or roadway. Adjacent departing lanes (not separated by an intervening approach leg) join together to form one-way departure legs, illustrated in FIG. 1 as extending to the north and to the south of the junction point. The arrows represent one-way inbound and outbound roadway segments which would attach to the one-way approach and departure legs, respectively, of the interchange and which would connect the interchange to other interchanges to form a roadway network. The arrows also indicate the direction of traffic flow and whether traffic is approaching (inbound to) or departing (outbound from) the junction.

FIG. 2 on Sheet 2/5 is a plan view depicting another embodiment of the invention: a Double Interpass (uninterrupted, grade-level interchange with two inbound one-way approach legs) with each of the approach legs having four lanes.

FIG. 3 on Sheet 3/5 is a plan view depicting yet another embodiment of the design, as an example, showing a Triple Interpass (uninterrupted, grade-level interchange with three inbound one-way approach legs) with each approach leg having two lanes.

FIG. 4 on Sheet 4/5 is a plan view depicting a grade-level transportation network having Double Interpasses (uninterrupted, grade-level interchanges, each with two inbound one-way approach legs) as the nodes of the network. The nodes (interchanges) would be connected by one-way roadway segments, represented by arrows showing the direction of traffic flow.

FIG. 5 on Sheet 5/5 is a plan view depicting a grade-level transportation network having Triple Interpasses (uninterrupted, grade-level interchanges, each with three inbound one-way approach legs) as the nodes of the network. The nodes (interchanges) would be connected by one-way roadway segments, represented by arrows showing the direction of traffic flow.

DETAILED DESCRIPTION OF THE INVENTION

The Interpass is a geometric design for a roadway junction that is entirely at-grade (nominally confined to a horizontal plane) and has any number, N, of one-way approach legs, such that N is an integer greater than or equal to two. The number of one-way approach legs classifies the junction as an “N-tuple”. For example, an Interpass junction having two approach legs is a “Double Interpass Junction”; one having three approach legs is a “Triple Interpass Junction”; one having four approach legs is a “Quadruple Interpass Junction”, and so forth, with each N-tuple interpass junction being a different embodiment of the subject invention.

Each approach leg may have any positive-integer number of lanes. The lanes of the approach legs—and of all roadways within the junction—must be hard lanes in order to prevent abrupt lane changes within the junction that could create conflict points or require abrupt directional changes or driver reactions.

The set of different embodiments of the invention includes all possible permutations of all possible combinations of numbers of approach legs and numbers of lanes composing each of the approach legs.

Described directionally from the viewpoint of flowing traffic, each approach leg bifurcates (splits) as it approaches the junction, with one or more lanes turning to the right, and one or more lanes turning to the left. The split can occur along a boundary between lanes, or could occur in the center of a lane such that the split lane becomes two lanes—one diverging left, and one diverging right. The boundary-split is preferred to the center-lane split, as the latter could, under certain circumstances, form a diverging conflict. If an inbound segment/approach leg has only a single lane, then its bifurcation must be a center-lane split. After each approach leg bifurcates, the lanes turning to the right continue to turn away from the junction point and become departure leg lanes, without crossing or merging with any other lane, as do those turning to the left. Adjacent departing lanes (those not separated by an intervening approach leg) are joined, without merging, as they depart the junction, to form a single, one-way departure leg. The total number of departure legs of the interchange should then equal the number of approach legs. The lanes of departure legs that join together must remain as hard lanes, with no two lanes converging into a single lane, for that could create a merging conflict.

Within the Interpass junction, all the roadways are one-way, all of the lanes are hard lanes, and no lane or roadway crosses or intersects with any other. As such, there are no conflict points, and traffic through the interchange can flow uninterrupted at uniform velocity. Also, because each approach leg has two departure legs from which a departure direction from the junction may be chosen, the Interpass is a well-connected interchange (minimum density 2). 

I claim:
 1. A geometric design, as described in the specification and drawings heretofore attached, for a roadway junction that: a. is entirely grade-level, b. has no conflict points, allowing uninterrupted, uniform-velocity traffic flow, c. may have any integer number, greater than or equal to two, of inbound, one-way approach legs, each approach leg having any positive-integer number of lanes, and d. provides at least two unique choices of outbound direction, via one-way departure legs, for each inbound approach leg.
 2. In reference to claim 1 of this section, each permutation of every combination of numbers of approach legs and numbers of approach leg lanes of the subject invention comprises a different embodiment of the invention. 